To prep boards by hand we need to choose an approach that’s suitable for the specific job, and doing this requires us to understand the wood, the tools and the project in question.
Despite the daunting amount of work, large projects can be surprisingly good practice when learning these skills because you can often get away with looser tolerances and still end up with a decent result. Practicing taking shavings is a good first stage when you’re new to hand planes, but I’d encourage you to experience things in the context of a project as soon as you can, because that’s when you’ll get a real grasp of things.
This video shows the surface prepping (or tarting up) for the underside of one of the top boards for my English Workbench. In this case the board has a big hump right down it’s centre. The board is very long and flexible so I needn’t worry too much about straightness along it’s length, and being the underside there’s also no need to aim for a perfect finish. So the goal here is to flatten the board along it’s width and remove that hump. A very slight cup down the centre would also be acceptable, but leaving any of that hump, even slightly would prevent the board from sitting flat upon the frame of the bench.
With this understanding of the intension of the piece, and it’s relation to other parts, you can govern your tolerance and know where you can loose it. This is not rough, but essential.
The full English Workbench Series is over five hours long, to learn more visit https://www.theenglishwoodworker.com/the-english-workbench/